Fuel valve and damper control for furnaces



April 14, 1936, T BRANCHE 2,037,363

FUEL VALVE AND DAMPER CONTROL FOR FURNACES Filed June 14, 1934 3 Sheets-Sheet l g 33 34 27 v. Muuuuuuuw I 32 2a a/ a ,7

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April 14, 1936. N. T. BRANCHE FUEL VALVE AND DAMPER CONTROL FOR FURNACES Filed June 14 1934 3 Sheets-Sheet 2 April 14, 1936. N BRANCHE 2,037,363

FUEL VALVE AND DAMPER CONTROL FOR FURNACES Filed June 14, 1954 5 Sheets-Sheet 3 I I M a 129.11. 5a 5,,

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Patented Apr. 14, 1936 FUEL VALVE AND DAMPER CONTROL FOR FURNACES Nelson T. Branche, Toledo, Ohio, assignor to Surface Combustion Corporation, Toledo, Ohio, a corporation of New York Application June 14, 1934, Serial No. 730,553

7 Claims.

This invention relates to control system for house heating furnaces which embody a damper in the exhaust flue and a motor operated fuel valve under the control of a room thermostat; and has for its general object to provide means for coordinating the operation of the fuel valve and damper in such a way that when the fuel valve is closed the exhaust damper will be closed and vice versa. The advantage of having the exhaust damper closed when the fuel valve is closed is that the escape of heat from the hot interior parts of the furnace to the exhaust flue or stack is materially reduced or effectually prevented. More particularly, it is an object of the invention to coordinate the operation of the fuel valve and exhaust damper in such a manner that when the room thermostat calls for heat the damper will be opened before the fuel valve is opened.

The invention has special utility in connection with gas fired furnaces but it may also be applied to oil fired furnaces.

Referring to the drawings wherein the preferred form of the invention is shown,

Fig. 1 is a side elevation of a warm air furnace equipped with the present invention;

Fig. 2 is an enlarged section on line 2-2 in Fig. 1 of the flue damper and associated mechanism;

Fig. 3 is an enlarged sectional view of the motor operated mechanism for operating the damper;

Fig. 4 is a detail view on line 4-4 in Fig. 3;

Fig. 5 is a sectional view on line 5-5 in Fig. 2;

Fig. 6 is a vertical sectional view showing parts of the valve operating mechanism;

Fig. 7 is a cross sectional view of the mechanism shown in Fig. 6;

Figs. 8, 9 and 10 are fragmentary detail views of parts associated with the valve operating mechanism, and

Fig. 11 is a diagrammatic representation of the electrical system for controlling the operation of the valve and damper operating mechanisms.

The furnace may be of any preferred type but is indicated as a warm air furnace ID. The burner for firing the furnace may also be of any preferred type but in the present instance is indicated as of a type having a portion II which extends outwardly from inside of the furnace, the fuel supply pipe being indicated at I2. Associated with the fuel pipe is a shut-off valve of any preferred type, the housing for which is indicated at I3, and associated with the valve is a motor mechanism the housing for which is indicated at I4. Leading from the furnace is an exhaust flue I 5 which leads to a stack not shown, and associated with the flue is a damper box I6. Associated with the damper is a motor mechanism, the housing for which is indicated at IT. Rt indicates a room thermostat and I8 and I8 the conduits for the wires of the various control circuits.

As shown in Figs. 2 and 5, the passage through the damper box is partially blocked off by a depending partition wall I9. The damper is indicated at 20 and is swingably supported at its upper edge by horizontal pivots 2|. When the damper is open it hangs vertically and its lower edge is then above the bottom of the box a sufficient distance to form a passage P therebetween for the flow of products of combustion from the burner within the furnace. The damper is preferably counterweighted as by a weighted arm 22 secured thereto and projecting above the common axis of the pivots 2 I. When the damper is closed 20 it assumes a. position at an angle to the vertical as indicated by dotted lines in Fig. 5, the bottom edge of the damper then abutting the adjacent end wall 23 of the damper box. Unless force is applied to hold the damper closed it tends to remain open.

Mounted on the damper is a vertical guide 24 for a crank 25 at one end of a crank arm 26 which forms part of a shaft 21. This shaft is connected through a gear train to an electric motor 28 (Fig. 3) supported on a chassis 29. The chassis is secured to one side of the damper box as by a lateral extension 30 which may be bolted or otherwise secured to said side, it being noted that the shaft 21 extends through said extension.

Mounted on chassis 29 are two spring blade switches SI and S2 (Fig. 3), one at either side of a gear 3| which is secured to the shaft 21 and which forms part of the gear train driven by the v motor 28. The contacts for the switches overlie the latter as indicated at S0. and Sb. The blades are so tensioned that the switches tend to remain open. Mounted on the shaft 21 for rotation therewith are two cams 32 and 33 for actuating the switches SI and S2, respectively. In Figs. 3 and 4 the cam 33 is shown as engaging and pushing the switch S2 against its contact Sb. A coil spring 34 on the shaft 2! will rotate the latter to close the damper when motor 28 is deenergized. The gear train between the shaft 21 and the motor 28 is a free running aifair hence the spring 34 in rotating the shaft 21 as said will also cause rotation of the gear train and motor in a damper-opening direction.

The motor mechanism for the gas valve will next be described. Detachably secured to the valve body I3 is a chassis 40 for supporting the valve operating mechanism. The valve stem is indicated at 4| and is shown as passing through a flexible seal 42. Pivotally mounted on the chassis as at 43 is a valve-operating lever 44 and pivotally mounted on the lever as at 45 is an upstanding link 46 having a hooked upper end as indicated at 41 (see Fig. 8). The lever 44 is pivotally connected as at 48 between the sides of a U-shape member 48 which is movably coupled to the valve stem 4|, the latter loosely passing through the bottom of the member and having thereon an adjustable nut 50 between which and another nut 5|, also on the valve stem, the said member is free to move. In other words, there is a lost motion connection between the said member 48 and valve stem 4|. The purpose of this'lost motion connection will more fully appear hereinafter.

Rotatably supported on the chassis 40 is a gear wheel 52 which is the last-driven gear of a gear train, the first gear of which is a pinion 53 secured to the shaft of an electric motor 54. Projecting laterally from one side of the gear 52 is a crank pin 55 for engaging with the hooked end 41 of the link 46 when the motor 54 is energized to open the valve or, in other words, when the gear wheel 52 is rotated in a clockwise direction as viewed in Fig. 8. A spring 56 associated with the lever 44 and link 48'tends to maintain the upper end of the link in a position to be engaged by the crank pin 55.

The gear train between the gear 52 and pinion 58 is a free running affair with the result that unless the motor 54 is positively prevented from rotating in a valve closing direction, as when it is energized, the valve will automatically close due to its being biased towards valve closing position by a spring, not shown, within the valve housing IS. The reverse rotation thus imparted to the gear train will ordinarily carry the crank pin 55 some distance away from the hooked end 41 of the link 45. The lost motion connection between the valve stem and U member 49 and the overrunning arrangement between the crank pin 55 on the gear wheel 52 and the link 46, singly and together, provide a slack coupling between the motor or prime mover 54 and the valve for a purpose hereinafter appearing.

In accordance with the present invention the gear wheel 52 is secured to a shaft 68 supported in appropriate bearings 6| and the shaft is made long enough, as indicated at 60a, to extend a substantial distance beyond one of the bearingsupporting standards 62 and beyond a panel board 83 secured to the standard in spaced relation. Mounted on the shaft extension for rotation therewith is a disk 64 having a radial flange 85 at one side. Turnably mounted on the disk is a switch-operating member 66 of insulating material. This member is frictionally held against the flange 65 by a spring-pressed plate 61 in order to insure that the member will turn with the disk. The degree that the member 66 is free to turn is limited by a stop pin 68, projecting from the standard 62 and extending between two fingers 59 projecting from the top of said member.

Mounted on the panel board 63 at one side of the member 66 is a fixed electrical contact '10. Pivotally mounted on said board as at H is an upstanding switch arm l2. Secured to theswitch arm and extending between said arm and the said member 88 is a light leaf spring 18 having a hump 14, this hump being arranged adjacent a wiper hump on the member. A light coil spring 16 anchored at one end to the panel board 88 and at its other end to the switch arm tends to pull the latter away from the contact I8 and holds the spring blade 18 in contact with the wiper hump 15 on the member 68. The arrangement is such that when the wiper member 66 is moved towards the right as viewed in Fig. 10, (in a valve opening direction) it will move the switch arm into engagement with its contact 18 against the tension of the coil spring l6. ,4,

Referring now to Fig. 11 which shows the wiring diagram for the apparatus: In this diagram the motor 54 of the valve-operating mechanism is assumed to be deenergized since the room thermostat is in a no-call-for-heat position which is equivalent to saying that the fuel valve is closed. In this position the damper motor 28 is energized to hold the damper closed. The circuit for the damper motor 28 is in such case starting and ending with its motor field 287 as follows: wires a, b and c; the secondary T2 of the transformer T; wire (1 to contact 10; contact 10 and switch arm 12 (for convenience of description these two elements may also be referred to as the third switch) and the 'wire e which completes the circuit.

When the damper motor 28 is energized to hold the damper 2!! closed, the switch elements SI, Sa (hereinafter also referred to as the fourth switch) make electrical contact by reason of the cam 32 pressing on the blade SI.

Assume now that the room thermostat Rt calls for heat as it does when its blades RI and R2 move to the right, as viewed in Fig. 11, into contact with terminals ,1 and h, respectively. (Blade RI and contact I will hereinafter also be referred to as first switch and blade R2 and contact h as second switch). The initial circuit for the valve motor 54 is then, starting and ending with its motor field 54f, as follows: wires 7' and c; the secondary T2 of the transformer T; wire d; switch elements l0, 12; wires 6 and k; switch elements SI, Sa; wire m; contact I; blade Rl to point n, and wires p and q to the motor field 54 The motor 54 upon being energized will continue to rotate until the cam 68 opens its associated switch 12, it being remembered that this opening occurs during the first few degrees of rotation of the shaft 60 ina valve-opening direction, or before all of the slack has been taken up between the crank pin 55 and the valve stem 4i. As soon as the switch 12 is opened, the power circuit for the damper motor 28 is opened whereupon the damper 20 immediately moves to open position under the influence of the spring 34 on the shaft 21. As the shaft 21 turns to damperopen position the cam 33 on said shaft closes the switch S2 (hereinafter also referred to as the fifth switch) and the cam 32 opens the switch Si.

The damper motor 28 having been deenergized to permit the damper to open, the valve motor 54 is again energized to permit it to open the fuel valve, the new circuit, starting with the motor field 54 being as follows: wiresa' and 0; secondary T2 of the transformer T; wire s, switch elements S2, Sb; wire 1. to the thermostat terminal h; blade Rl to point n, and wires 1) and q to the motor field 54f. The motor 54 after having opened the fuel valve is allowed in accordance with the present circuit. to remain energized to aoeaees hold the valve open until the thermostat Rt moves to no-call-for-heat position.

While not shown in the diagram, a switch un== der the control of a pilot thermostat will be provided at some appropriate point as at a: to pre vent the motor 54 from being energized unless the pilot is burning.

What I claim is:

1. In a control system for a furnace having a damper in its exhaust flue and a fuel control valve, the combination of five switches, a thermostat comprising the first and second of said switches both of which are closed when the thermostat calls for heat, a mechanism for operating said valve and comprising the third of said switches and a motor for operating said mechanism in a valve-opening direction, said third switch being closed by said mechanism on initial movement of the latter in a valve-closing direction and being opened by said mechanism on initial movement of the latter in a valve-opening direction, a mechanism for operating said damper and comprising the fourth and fifth of said switches and a motor for operating the mechanism in a damper-closing direction, the fourth of said switches being closed when the damper is closed and the fifth of said switches being closed when the damper is open, a circuit comprising the third of said switches and being active to energize the motor of the damper-operating mechanism when the said third switch is closed, a circuit comprising the first, third and fourth of said switches and being active to energize the motor of the valveoperating mechanism when the said first, third and fourth switches are closed, and a circuit comprising the second and fifth of said switches and being active to energize the mdtor oi the valve-operating mechanism when said second and fifth switches are closed.

2. In a control system for a furnace having a damper in its exhaust fine and a fuel control valve, the combination of mechanism for operating said valve, 9, switch associated with said mechanism and operated by the latter to closed position on initial movement of the mechanism in a valve-closing direction and operated by the mechanism to open position on initial movement of the mechanism in a valve-opening direction, means including a motor for closing said damper when the motor is energized, and a circuit com prising said switch for energizing said motor when said switch is closed.

3. In the combination specified in claim 2, the said mechanism comprising a free -running gear train and a motor for operating the latter in a valve-opening direction.

4. In a control system for a furnace having a damper in its exhaust flue biased towards open position and a fuel control valve, the combination of a power-operated device associated with said damper and normally energized to hold the damper closed while the fuel valve is closed, a prime mover for opening the valve, a coupling connecting the prime mover and valve in a manner to provide a limited degree of slack therehetween, a master controller for energizing the prime mover, and means operable while the prime mover is taking up the slack between it and the valve for deenergizing the said power-operated device whereby the damper may open before the valve is opened by the prime mover.

5. In a control system for a furnace having a damper in its exhaust flue and a fuel-supply device, in combination, movable means for actuating the fuel-supply device, means for opening the damper operated by initial movement of the movable means, and'means for rendering the movable means inoperative during intermediate movement of the damper.

6. in a control system for a furnace having an exhaust fine and a fuel-supply device, in combination, a damper in the exhaust flue biased toward open position, means for actuating the fuelsupply device, means for releasing the damper operated by the device-actuating means, and means for rendering the device-actuating means operative while the damper is in closed and opened positions and inoperative while the damper is in intermediate positions.

7. In a control system for a furnace having a damper in its exhaust flue and a fuel-supply device, in combination, means for actuating the fuel-supply device, means for opening the damper operated by the device-actuating means, means for rendering the device-actuating means oper ative while the damper is closed, means for ren-= dering the device-actuating means inoperative upon operation of the damper-opening means, and means actuated when the damper is fully open for rendering the device-actuating means again operative.

NELSON T. BRANCHE. 

